1. Skeletal System Overview: “skeleton” Greek for “dried up body”
Designed for protection and motion
The skeleton is a tower of bones arranged in a way we can stand upright and balance

2. The skeleton is divided into two divisions:
Axial skeleton
Bones that form the longitudinal axis of the body
Head, thorax
Appendicular skeleton
Bones of the limbs and girdles
Hips, arms, hands, legs and feet
Also includes:
Joints, cartilages and ligaments

3. Functions of the Bones Support
form internal framework that supports and anchors all soft organs.
Legs provide for support for our axial skeleton
Rib cage supports the thoracic wall

4. Protection Provide protection for all soft organs
Skull::brain; rib cage::lungs, heart; vertebrae::spinal cord

5. Movement:
Skeletal muscles attached to bones via tendons allow for movement of the skeletal system.

6. Storage:
Bones provide a means of storing fats, minerals (Calcium and phosphorus)
“deposits” and “withdrawals” of calcium to and from bones take place all the time

7. Blood cell Formation:
a.k.a hematopoiesis, occurs within the marrow of certain cavities of certain bones.

8. Classification of Bones
206 bones in adults
Two basic types of osseus or bone tissue:
Compact bone is dense and looks smooth and homogenous
Spongy bone is composed of small needlelike pieces of bone and lots of open space.
Bones come in a variety of shapes and sizes
The unique shape of each bone fulfills a particular need.

9. Bone Classification: Shape
Bones are classified according to shape into four groups:
Long
Short
Flat
Irregular

10. Long Bones Typically longer than they are wide
Composed of a shaft with a head at each end
Mostly compact bone
All bones of the limbs other than wrist and ankles

11. Short Bones Generally cube-shaped Contain mostly spongy bone
Wrist and ankles contain short bones
Sesamoid bones, form with tendons (kneecap)

12. Flat Bones Thin, flattened and usually curved
Two thin outer layers of compact bone with a layer of spongy bone between them
Ribs, sternum and most bones of the skull

13. Irregular Bones Bones that do not fit one of the preceding categories
Vertebrae and hips are examples

14. Structure of a Long Bone
Diaphysis or shaft
Makes up most of the bones length
Compact bone
Covered and protected by a fibrous connective tissue membrane called periosteum
The periosteum is secured to the bone by many connective tissue fibers Sharpey’s fibers.

15. Epiphyses are the ends of the long bone
Compact bone enclosing an area filled with spongy bone
Covered with articular cartilage
Articular cartilage (hyaline cartilage) it provides a smooth, slippery surface to reduce friction in joints
In adult bones, a thin line of bony tissue throughout the epiphysis that is different in appearance. This is called the epiphyseal line, which is a remnant of the epiphyseal plate – a flat late of hyaline cartilage, cause the lengthwise growth of long bones.
E. P. – completely replaced by bone at the end of puberty

16. In adults the cavity of the shaft is a primary storage for adipose tissue
a.k.a. yellow marrow, or medullary cavity
In infants this area forms blood cells and red marrow is found in the cavity
In adults, red marrow is confined to the cavities of spongy bone of flat bones and the epiphyses of some long bones

17. Bone Markings
Bones are noticeably rough and scarred with bumps, holes and ridges.
The markings reveal where the attachment of muscles, tendons and ligaments attach and where blood vessels and nerves passed.
Two categories:
Projections or Process – grow out from the bone surface (all markings that begin with “t”)
Depressions or Cavities – indentations in the bone (all markings that begin with “f” except facet)